We have the brains of worms

Way back in the early 19th century, Geoffroy St. Hilaire argued for a radical idea, that vertebrates and most invertebrates were inverted copies of each other. Vertebrates have a dorsal nerve cord and ventral heart, while an insect has a ventral nerve cord and dorsal heart. Could it be that there was a common plan, and that one difference is simply that one is upside down relative to the other? It was an interesting idea, but it didn’t hold up at the time; critics could just enumerate the multitude of differences observable between arthropods and vertebrates and drown out an apparent similarity in a flood of documented differences. Picking out a few superficial similarities and proposing that something just looks like it ought to be so is not a persuasive argument in science.

Something has changed in the almost 200 years since Geoffroy made his suggestion, though: there has been a new flood of molecular data that shows that Geoffroy was right. We’re finding that all animals seem to use the same early molecular signals to define the orientation of the body axis, and that the dorsal-ventral axis is defined by a molecule in the Bmp (Bone Morphogenetic Protein) family. In vertebrates, Bmp is high in concentration along the ventral side of the embryo, opposite the developing nervous system. In arthropods, Bmp (the homolog in insects is called decapentaplegic, or dpp) is high on the dorsal side, which is still opposite the nervous system. At this point, the question of whether the dorsal-ventral axis of the vertebrate and invertebrate body plans have a common origin and whether one is inverted relative to the other has been settled, and the answer is yes.

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Kevin Padian explains macroevolution

The gang at the NCSE have put together Padian’s testimony at the Dover trial with the slides he used. You may have already read the transcript, but with the figures added it acquires a whole new dimension — it’s basically a wonderfully done primer in the basics of macroevolutionary biology. Next time some creationist tries to simper at you that he accepts microevolution, but that there’s no evidence for macroevolution and he refuses to believe it, point him at this page. It’s aimed not at scientists, but at the judges and lawyers at a trial, so it’s eminently comprehensible to any intelligent layman … and it crushes the bogus rejection of macroevolution that they are so fond of using.

Twisty maze of duck oviducts

I’m sure you’ve already heard about it, so I’m a little redundant to bring it up — Carl Zimmer has a spiffy article in the NY Times about duck phalluses. No, that’s not quite right; the most interesting part of the story was the bit about duck oviducts. Female ducks have been evolving increasingly convoluted oviducts to baffle the efforts of duck rapists to inseminate them, and male ducks have been evolving concomitantly long phalluses to thread the maze and deliver sperm to the ovaries.

I’d heard about these huge intromittent organs in ducks before, but this is another fascinating revelation: it took a woman scientist to suggest that maybe, just maybe, they also ought to look at what’s going on in the female ducks, and then the whole wonderful story of coevolution of these structures emerged. It’s actually a rather embarrassing instance of a scientific blind spot, where the biases of the investigators led them to overlook an important component of the story.

Conway Morris at Baylor

This is cool: Simon Conway Morris gave a talk at Baylor, and Cody was there. Conway Morris is a smart fellow who does some very interesting work, and now I learn that he’s also a charming speaker — even though I completely disagree with his conclusions, I wish he’d come a little farther north so I could listen to him. I’d most like to hear him talk about Cambrian and pre-Cambrian paleontology, but it sounds like he’s instead lecturing specifically on the ideas where he’s most wrong, his belief in the overwhelming power of natural selection (or perhaps, design) to drive convergence. Convergence happens, of course, but Conway Morris seems to favor sifting the evidence for similarities and ignoring the differences, and divergence happens, too.

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Simon Conway Morris and Life’s Solution: it’s tea.

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I’ve finished Simon Conway Morris’s Life’s Solution: Inevitable Humans in a Lonely Universe(amzn/b&n/abe/pwll), a book I’ve mentioned before and promised, with considerable misgivings, to read thoroughly. I didn’t like his ideas, I thought he’d expressed them poorly before, but I’d give his book on the subject a fair shake and see if he could persuade me.

My opinion: it’s dreck.

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Hagfish embryos!

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A hagfish egg with a 14.3-mm pharyngula-stage embryo inside (arrows). Scale bar, 5 mm.

I’ve been looking forward to seeing these little jewels in print since I saw Kuratani talk about them at the SICB meetings in January. Hagfish are wonderfully slimy jawless chordates that have been difficult to raise in the lab—although if you poke a whale corpse rotting in the cold deeps you’ll find them swarming everywhere. The Kuratani lab has managed to keep animals of the species Eptatretus burgeri alive and healthy in a lab aquarium maintained at cold temperatures (16°C), and has even had success in breeding them. That object to the right is a single hagfish egg, brown and leathery-shelled and surprisingly big—it’s an inch and a half long!

They collected 92 eggs, and then another limitation emerged: it took 5-7 months for embryos to develop in a small number of the eggs. Hagfish aren’t going to be your typical fast-developing model system, I’m afraid, but they are extraordinarily cool animals, and it’s good to see work beginning on them.

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Wells’ flagrantly false commentary on Hox complex structure

This evening, I am watching an episode of that marvelous and profane Western, Deadwood, as I type this; it is a most excellently compensatory distraction, allowing me to sublimate my urge to express myself in uncompromisingly vulgar terms on Pharyngula. This is an essential coping mechanism.

I have been reading Jonathan Wells again.

If you’re familiar with Wells and with Deadwood, you know what I mean. You’ll just have to imagine that I am Al Swearingen, the brutal bar-owner who uses obscenities as if they were lyric poetry, while Wells is E.B. Farnum, the unctuous rodent who earns the contempt of every man who meets him. That imagination will have to hold you, because I’m going to restrain myself a bit; I’m afraid Wells would earn every earthy sobriquet I could imagine, but I’ll confine myself to the facts. They’re enough. The man completely misrepresents the results of a paper and a whole discipline, and does it baldly on the web, as if he doesn’t care that his dishonesty and ignorance leave a greasy, reeking trail behind him.

Let’s start with Wells’ own words.

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Those disreputable evo-deviants and their bigotry against the single-celled

I must disagree with Larry Moran, who accuses the field of evo-devo of animal chauvinism — not that it isn’t more or less true that we do tend to focus on metazoans, but I disagree with an implication that this is a bad thing or that it is a barrier to respectability. Larry says we need to cover the other four kingdoms of life in greater breadth, which I agree is a fine idea. I would like to have a complete description of the genome of every species on earth, a thorough catalog of every epistatic interaction between those genes during development, a hundred labs working on each species, and a massive collection of papers for each one documenting every step and every protein and every variation in their development. I would like it tomorrow.

I think we all agree that that would be impractical. The question is how we will focus our research to maximize our use of limited resources, and get us useful answers that will lead us in productive directions. Larry is advocating maximizing our phyletic breadth by following organisms representative of the greatest amount of diversity. He is proposing this in opposition to the proposal from Jenner and Wills, who suggest a different strategy — and I find myself agreeing more with Jenner and Wills than with Moran.

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